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ABSTRACT A new small diameter sampler with two chamber hydraulic pistons (45 sampler) has been developed, and its applicability is examined though the unconfined compression tests and the standard oedometer tests. The quality of samples obtained from the 45 sampler is higher than those of the sampler normally employed in Japan for both Holocene and Pleistocene clay deposits. INTRODUCTION A new small diameter sampler with two chamber hydraulic pistons (45 sampler) was developed, and its applicability is examined through the unconfined compression tests and the standard oedometer tests for samples obtained from Holocene and Pleistocene clay deposits. In an engineering sense, there is no difference in shear strength and deformation characteristics between the S specimen (15 mm in diameter (d) and 35 mm in height, (h)) and the O specimen (35 mm in d and 80 mm in h), which are examined for soils of the plasticity index (Ip) from 17% to 98%. unconfined compressive strength (qu) from 20 kPa to 1000 kPa. overconsolidation ratio (OCR) from 0.7 to 78, and different sites (Shogaki. 1991" Shogaki et al. 1993). Ten S specimens can be taken from a sample. 75 mm in d and 50 mm in h, sampled from the sampler (75 sampler) normally employed in, Japan as the Japanese Geotechnical Standard for the method for obtaining undisturbed soil sample using a thin-walled tube sampler with fixed piston (JGS 1221–1995). Of the ten specimens, the stress-strain curves of specimens located version close to the sampling tube wall are similar to those of specimens located in the central site of the plane of the sampling tube (Shogaki et al. 1995). This fact suggests the possibility of the development of a small diameter sampler and its applicability in practice. The new 45 sampler was developed from this information.
- Phanerozoic > Cenozoic > Quaternary > Pleistocene (0.50)
- Phanerozoic > Cenozoic > Quaternary > Holocene (0.50)
ABSTRACT In order to use the advantages of unconfined compression tests, a new testing procedure in the field is proposed and a new portable unconfined compression test apparatus with suction measurement is outlined. From laboratory data, the effect of specimen size on unconfined compressive strength properties for natural clay deposits are discussed. In an engineering sense, it was proved that there was no difference in shear strength and deformation characteristics between the S (or Small size) specimen (15 mm in diameter (d) and 35 mm in height (h)) and the O (or Ordinary size) specimen (35 mm d and 80 mm h), which were examined for soils having plasticity indexes (I p) from 17 % to 150 % and unconfined compressive strengths (q u) from 20 kPa to 1000 kPa and at nineteen different sites in the United Kingdom, Korea and Japan. INTRODUCTION The unconfined compressive strength (q u) is widely used for the stability analysis of clay foundations under undrained condition in Japan. This is mainly because the average value of q u/2 well describes the undrained shear strength on a failure surface in a ground in total, and in addition to this, the testing procedure for the q u-value is simple. The specimen size usually used in Japan for unconfined compression test (UCT) is the O (or Ordinary size) specimen (35 mm in diameter (d) and 80 mm in height (h)). However, for O specimens, the number of specimens required is remitted and their preparation for testing is difficult due to latent cracks or inhomogenity. Therefore, the small size specimen is better for effective use of samples because the cross sectional area of the specimen is about 10 cm2 and it is not necessary to retain it since calculations and measurements can be done via automatic electronic instruments.
ABSTRACT: To improve the reliability of design for the slope stability under the ø =0 condition, the effect of sample disturbance on undrained strength anisotropy was investigated through laboratory testing. In the case of the undisturbed sample, the ratios of the undrained strength of the horizontal specimen to that of the vertical specimen are within the range of 0.61-0.84. The relationship between undrained strength anisotropy and sample disturbance is given as a function of the ratio of qu values of the disturbed sample to that of the undisturbed sample, quratio. The undrained strength anisotropy is lapsed for degrees of disturbance that decrease undrained shear strength by fifty percent. INTRODUCTION An undrained failure occurring in a deposit of clay in the field has a shear strength on the failure surface depending on the orientation of the surface, resulting from either the anisotropy of the clay or the reorientation of principal stresses. Therefore, the measurement of the undrained strength anisotropy is important to investigate the effect of anisotropy on the conventional factor of safety in the design of earth slopes. To improve the reliability of design for the slope stability under the ø =0 condition, the effects of sample disturbance and effective stress behavior on undrained strength anisotropy was investigated through laboratory testing. The sample disturbances were made by the extruder after setting up the disturbing equipment on the edge of the sample tube (Shogaki and Kaneko,1993). The dimensions of the specimens used for the unconfined compression test were" 15 mm in diameter and 35 mm in height. These specimens, prepared by the ordinary tube sampler, will demonstrate the anisotropy of strength, of which the major principal stress is at an angle of inclination, 8, to the vertical (ShogakL et a1.,1994).
ABSTRACT: The statistical properties of soil data within thinwalled samplers of an alluvial marine clay deposit were investigated with an unconfined compression test, using small specimens 15 mm in diameter, S specimen, and a portable unconfined compression test apparatus. In the case of the stationary piston sampler widely used in Japan. It was 75 mm in inner diameter and 1000 mm in length. The range of sample disturbance caused by the penetration of the sampling tube and the extrusion of soil samples are within about 2 mm of the wall of the sampler. The effect of sample disturbance within thinwalled samplers is small, in the range of <100-600) mm from the edge of the sampling tube. INTRODUCTION There is a growing tendency toward the rationalization of design such as the reliability-based design and the limit-state design for soils and foundations engineering. In these design methods, the accuracy of estimation of soil properties ruled the reliability of design. But these measured values do not necessarily represent soils within thinwalled samplers, because these soil data are limited to both the site within a sample and the number of tests. It is as a basis for the soil investigation and the design that the statistical properties of soil within a sampler and the position of measured values are made clear. The statistical properties of soil data within thinwalled samplers of an alluvial marine clay deposit were investigated by an unconfined compression test, using small specimens 15 mm in diamet er, S specimen, and a portable unconfined compression test apparatus (Shogaki1991). The number of specimens was about one hundred and fifty for a thinwalled sampler. S specimens and ordinary size specimens 35 mm in diameter, 0 specimen, display a similar strength and deformation behavior for Amagasaki and Urayasu alluvial marine clay.
ABSTRACT Sample disturbance caused by tube penetration in sampling is examined based on pore water pressure behavior, void ratio and movement of soil particles caused by tube penetration. The 35 mm, 45 mm and 75 mm samplers, having 6° or 90° cutting edge angles, are used for model tests in Toyoura sand. The penetration speeds are in the range of 0.5 cm/sec to 5.4 cm/sec. The relative density is in the range of 30 % to 50 %. All inner tube soil particles, with the exception of an area close to the tube wall, shifted simultaneously due to that area achieving plasticity, thus acting as a lubricant. This coincides with microstructure and strength properties of clay.